sem_getvalue(3p) — Linux manual page

SEM_GETVALUE(3P)        POSIX Programmer's Manual       SEM_GETVALUE(3P)

PROLOG

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME

       sem_getvalue — get the value of a semaphore

SYNOPSIS

       #include <semaphore.h>

       int sem_getvalue(sem_t *restrict sem, int *restrict sval);

DESCRIPTION

       The sem_getvalue() function shall update the location referenced
       by the sval argument to have the value of the semaphore
       referenced by sem without affecting the state of the semaphore.
       The updated value represents an actual semaphore value that
       occurred at some unspecified time during the call, but it need
       not be the actual value of the semaphore when it is returned to
       the calling process.

       If sem is locked, then the object to which sval points shall
       either be set to zero or to a negative number whose absolute
       value represents the number of processes waiting for the
       semaphore at some unspecified time during the call.

RETURN VALUE

       Upon successful completion, the sem_getvalue() function shall
       return a value of zero. Otherwise, it shall return a value of -1
       and set errno to indicate the error.

ERRORS

       The sem_getvalue() function may fail if:

       EINVAL The sem argument does not refer to a valid semaphore.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       semctl(3p), semget(3p), semop(3p), sem_post(3p),
       sem_timedwait(3p), sem_trywait(3p)

       The Base Definitions volume of POSIX.1‐2017, semaphore.h(0p)

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version and the original IEEE and The
       Open Group Standard, the original IEEE and The Open Group
       Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                  SEM_GETVALUE(3P)

Pages that refer to this page: semaphore.h(0p), semctl(3p), semget(3p), semop(3p)

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